Hi a would like to create a distribution list on my exchange server 2007 for all the mailbox in exchange organization to send information for only the the people in our company, now we don´t like to a external email arrive to this distribution list, for security reason. How can configure this requirement for only internal communication. Regards

On the Mail Flow Settings | Message Delivery Restrictions for the group, check the box that says "Require that all senders are authenticated"[string](0..33|%{[char][int](46+("686552495351636652556262185355647068516270555358646562655775 0645570").substring(($_*2),2))})-replace " "